Conversion of biomass feedstocks into hydrocarbon liquid transportation fuels

ABSTRACT

Methods for converting a carbon-containing feedstock into a fluid transportation fuel are described. The methods may include converting the carbon-containing feedstock into a producer gas comprising H 2 , CO, CO 2 , and N 2 , and reacting the producer gas with a substrate catalyst to produce a combination of Fischer-Tropsch (F-T) products, the F-T products including the fluid transportation fuel. A portion of the F-T products may be catalytically cracked to produce additional amounts of the fluid transportation fuel. A portion of the F-T products may also be hydrogenated to produce additional amounts of the fluid transportation fuel. Apparatuses are also described or converting a carbon-containing feedstock into a fluid transportation fuel. The apparatuses may include a producer gas reactor, a Fischer-Tropsch reactor, a cracking reactor, and a hydrogenation reactor.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/087,327, filed Aug. 8, 2008, the entire contents of which is hereinincorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

Commercial Gas-to-Liquid (GTL) systems for converting natural gas to into hydrocarbon liquid transportation fuels are often based on amultiplicity of complex refinery-based operations using oxygen-blownconversion of natural gas (or other fossil fuel-based resources) intosynthesis gas (a.k.a. syngas) containing hydrogen (H₂) and carbonmonoxide (CO). The syngas is converted into liquid hydrocarbon fuels andwaxes through a series of Fischer-Tropsch Synthesis (FTS) reactions thatare catalytically activated by a transition-metal based catalyst. Themain FTS reaction is the conversion of hydrogen and carbon monoxide intothe liquid hydrocarbon fuel and water:

[Reaction 1]

nCO+2nH₂

—{CH₂ }—+nH₂O  [1]

As Reaction 1 shows, each molecule of CO requires two molecules of H₂ toproduce hydrocarbon products (liquid fuels and waxes) and one moleculeof water (H₂O). In Biomass to Liquid (BTL) systems, the gasification ofbiomass to produce a hydrogen-deficient syngas (containing anapproximately 1:1 mole ratio of CO:H₂) cannot sustain Reaction 1. Thus,for BTL systems, the CO:H₂ ratio may be adjusted through theWater-Gas-Shift (WGS) reaction to convert a portion of the water vaporand CO in the gasified biomass to additional H₂ with CO2 as a byproduct:

[Reaction 2]

CO+H₂O

H₂+CO₂  [2]

In many BTL systems, the WGS reaction is catalyzed by an iron-basedFischer-Tropsch catalyst so that approximately one-half the CO in thegas reacts with an equal molar amount of water vapor (which may besourced from the Reaction 1) to produce H₂ and CO. The remaining CO isconverted to FTS products.

In most large-scale GTL and BTL systems, highly-polished syngas(containing only CO and H₂) is converted to heavy paraffinic FTS waxesat pressure of 250 to 400 psig. In a series of refinery-basedoperations, the FTS wax products are cracked and hydrogenated intogasoline and diesel-fuel products. These GTL facilities are usually verylarge (typically producing several thousands of barrels per day ofdiesel product) and demand on-site oxygen and hydrogen generation plantsto support the gasification and fuel upgrading systems.

Unfortunately, large-scale GTL and BTL systems require significantinvestments of capital to build. They also need to receive the properapprovals from regulatory, environmental, and zoning authorities thatcan limit the ability to build these systems near the biomass sourcesthey will utilize to make the FT fuels. The systems also need to becoupled to or located near fuel transportation infrastructure to deliverthe FT fuels to their final destination (e.g., gas stations). Given thelarge investment of capital and difficult source to end use logisticsthat are typical for these large scale systems, there is a need for newmethods and systems to generate FT fuels.

BRIEF SUMMARY OF THE INVENTION

The conventional wisdom is that a small biorefinery would have pooreconomics. However, a small-scale biorefinery allows the use of low, oreven negative cost feedstocks at their source, thereby reducing or eveneliminating transportation and distribution costs. This small-scaleparadigm, in conjunction with a greatly simplified conversion process,will allow the quick establishment of small-scale biorefineries inlocations where comparative fuels are expensive.

Small, modular liquid fuel generation and processing systems aredescribed for generation of liquid FT fuels on-site. The processes andsystems may include the generation of producer gas from a combination ofgasified biomass and air that may converted to FT liquid fuels. Theprocesses and systems may also include refining the initial FT productsinto liquid fuel products such as gasoline, diesel, and/or aviationfuel. These small-scale processes and systems are small fraction of thesize and cost of conventional commercial GTL and BTL systems.

Embodiments of the invention include methods for converting acarbon-containing feedstock into a liquid transportation fuel. Themethods may include converting the carbon-containing feedstock into aproducer gas comprising H₂, CO, CO₂, and N₂, and reacting the producergas with a substrate catalyst to produce a combination ofFischer-Tropsch (F-T) products, where the F-T products including theliquid transportation fuel. The methods may also include the step ofcatalytically cracking a portion of the F-T products to produceadditional amounts of the liquid transportation fuel. In addition, themethods may include hydrogenating a portion of the F-T products toproduce additional amounts of the liquid transportation fuel.

Embodiments of the invention also include apparatuses for converting acarbon-containing feedstock into a fluid transportation fuel. Theapparatuses may include a producer gas reactor operable to convert thecarbon-containing feedstock into a producer gas comprising H₂, CO, CO₂,and N₂. The apparatuses may also include a Fischer-Tropsch reactorfluidly coupled to the producer gas reactor, where the Fischer-Tropschreactor is operable to convert a portion of the producer gas into acombination of Fischer-Tropsch (F-T) products, and where the F-Tproducts including the fluid transportation fuel. The apparatuses mayalso include a cracking reactor fluidly coupled to the Fischer-Tropschreactor, where the cracking reactor is operable to catalytically crack aportion of the F-T products to produce additional amounts of the fluidtransportation fuel. In addition the apparatuses may include ahydrogenation reactor fluidly coupled to the cracking reactor, where thehydrogenation reactor is operable to hydrogenate a portion of the F-Tproducts to produce additional amounts of the fluid transportation fuel.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the invention. The features and advantages ofthe invention may be realized and attained by means of theinstrumentalities, combinations, and methods described in thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings wherein like reference numerals are usedthroughout the several drawings to refer to similar components. In someinstances, a sublabel is associated with a reference numeral and followsa hyphen to denote one of multiple similar components. When reference ismade to a reference numeral without specification to an existingsublabel, it is intended to refer to all such multiple similarcomponents.

FIG. 1 is a simplified schematic showing selected components of anapparatus for converting carbon-containing feedstocks to fluidtransportation fuels according to embodiments of the invention; and

FIG. 2 is a flowchart showing selected steps in a method of convertingcarbon-containing feedstocks to fluid transportation fuels according toembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Methods and systems are described for converting carbon-containingfeedstocks to fluid transportation fuels such as gasoline, diesel, andavaition fuel, among other transportation fuels. The carbon-containingfeedstocks may include biomass (e.g., woodchips) that is gasified in thepresence of air to make a producer gas that includes hydrogen (H₂),carbon monoxide (CO), carbon dioxide (CO₂), and nitrogen (N₂). Thenitrogen is largely supplied by the air, and may account for about 50mol. % of the producer gas.

The producer gas may be sent directly to a Fischer-Tropsch reactorwithout first passing through an air separation unit to eliminate thefree nitrogen. It has been surprisingly discovered that the freenitrogen in the producer gas does not interfere with the functioning ofthe Fischer-Tropsch catalyst, and can even stabilize the productionrates of the F-T products by acting as a temperature moderator. The heatcapacity of the free nitrogen can also allow larger diameter F-Treactors (e.g., about 2 to about 3½ inches in diameter versus about 1inch for convention F-T reactors) without concerns of runawaytemperatures.

The Fischer-Tropsch catalyst may also be selected or treated to catalyzean in-situ water-gas-shift reaction in the producer gas. Producer gasmade from biomass feedstocks typically has a CO:H₂ ratio of about 1:0.7,while the ratio should be closer to about 1:2 to sustain the productionof F-T products. When the Fischer-Tropsch catalyst can catalyze a WGSreaction, the adjustment of the CO:H₂ ratio can take place at the F-Tcatalyzation site instead of in a physically separated WGS reactor.

The size of the present apparatuses are significantly smaller thanconventional Fischer-Tropsch systems, and may be small enough forportable operations that are co-located with a biomass feedstock source(e.g., wooded area) and/or transportation fuel depot such as a garage,gas-station, marina, airport, etc. This can significantly reduce thecosts and energy needed to transport the carbon feedstock to theapparatus, and the fuel made by the apparatus to the end-usetransportation vehicle. Further details of embodiments of the presentapparatuses and methods are given below.

Exemplary Apparatuses

FIG. 1 shows a simplified schematic of selected components of anapparatus 100 for converting carbon-containing feedstocks to fluidtransportation fuels according to embodiments of the invention. Theapparatus 100 may include a producer gas reactor 102 that mixes acarbon-containing feedstock with air to make a producer gas. Thefeedstock may include gaseous, liquid or solid hydrocarbons. Examples ofthese hydrocarbons include coal, peat, heavy oil, light olefinhydrocarbons, natural gas, methane, ethane and/or other gaseous orliquid alkanes, alkenes, or alkynes.

The producer gas reactor 102 may also be a gasification reactor thatconverts carbon-containing biomass and air into producer gas. Thisbiomass may include woody biomass, non-woody biomass, cellulosicproducts, cardboard, fiber board, paper, plastic, and food stuffs amongother biomass. Biomass may also include human refuse that can have anegative cost as the refuse suppliers actually pay to have the refuseremoved from a premises (e.g., a waste dump). Many types of biomass havelow levels of sulfur and heavy metal contaminants compared toconventional hydrocarbon fuel sources like oil and coal. The moisturecontent of the biomass may be adjusted to about 5 wt. % to about 20 wt.% (e.g. about 15 wt. %) and placed in the gasification reactor where itis heated in the presence of air to form the producer gas.

When the feedstock is biomass, the producer gas may be a product of thepyrolysis of the biomass with molecular oxygen (O₂) from the suppliedair. This is a controlled partial combustion process designed topartially oxidize the largest portion of the biomass into H₂ and COinstead of fully oxidized H₂O and CO₂ (although both these gases arepresent in the producer gas). An example of a modular biomassgasification reactor that may be incorporated into embodiments of theapparatus is described in U.S. patent application Ser. No. 11/427,231,filed Jun. 28, 2006 and titled “Method And Apparatus For Automated,Modular, Biomass Power Generation”, the entire contents of which areherein incorporated by reference for all purposes.

The free nitrogen (N₂) from the air is relatively unreactive with thecarbon-containing feedstock, and mostly remains as free nitrogen in theproducer gas. Air is about 78 mol. % N₂, and the free nitrogen mayaccount for about 50 mol. % of the producer gas. Typically, conventionalF-T GTL and BTL systems separate most or all of the free nitrogen, inthe producer gas using an air separation unit (ASU) and only send thepurified producer gas (usually called syngas) to a F-T reactor 104.However, it has been surprisingly discovered that separating the freenitrogen is not necessary, and that the unpurified producer gas may besent directly to the F-T reactor 104.

The F-T reactor 104 may include a substrate catalyst to convert CO andH₂ into F-T products as shown in Reaction 1 above. The substratecatalyst may be a transition metal and/or transition metal oxide basedmaterial such as iron and/or an iron oxide. Examples of iron-containingminerals used in the catalyst substrate include magnetite and hematite,among other minerals. The substrate catalyst may also be selected and/ortreated so that it will also catalyze an in-situ water-gas-shift (WGS)reaction (see Reaction 2) to tip the ratio of CO:H₂ towards 1:2. Forexample, when the substrate catalyst is an iron-containing catalyst, itmay be treated with a copper or potassium promoter that also makes it aWGS reaction catalyst. The substrate catalyst may also be exposed to areducing atmosphere to activate F-T reaction sites on the substratecatalyst.

As noted above, when the nitrogen (N₂) is left in the producer gas itsheat capacity may allow larger amounts of the F-T substrate catalyst tobe packed into the F-T reactor 104. For example, the diameter of thetube holding the substrate catalyst may be about 2 to about 3½ inches indiameter compared to about I inch for conventional BTL systems. Theproducer gas may flow through this tube at a temperature of about 250°C. to about 300° C. The nitrogen may also allow the F-T reactor 104 tooperate at lower pressure of about 250 psig or less (e.g., 150 psig)compared to conventional BTL systems which operate closer to about 300psig.

The F-T products generated by the F-T reactor 104 may include the fluidtransportation fuels such as gasoline, synthetic paraffinic kerosene(SPK), diesel fuel, and avaition fuel. The F-T products may also includesmaller hydrocarbons such as methane, ethane, propanes, butanes, lightolefins (e.g., ethylene, propylene and butelenes), etc., as well aslarger hydrocarbons such as paraffinic waxes. These smaller and largerproducts may be converted into additional fluid transportation fuels bythe cracking reactor 106 and the hydrogenation reactor 108.

A hot wax trap 105 may be optionally coupled to the F-T reactor 104.This trap captures hydrocarbon waxes that make up part of the F-Tproducts. The trap 105 may be configured for the recovery of the waxes,which are also useful F-T products.

The cracking reactor 106 may catalytically crack the larger hydrocarbons(e.g., waxes) into fluid transportation fuels and may also condenseunsaturated carbon-carbon bonds in, for example, light olefins to makealkyl substituted aromatic fluid transportation fuels. The crackingprocess may reduce the amount of larger, waxy hydrocarbon F-T productsfrom about 20 wt. % to less than 5 wt. %.

The cracking reactor 106 may include a cracking catalyst, such as aZSM-5 synthetic zeolite (e.g., H-ZSM-5). These zeolites are availablecommercially as a generic commodity product. For example, a suitablezeolite used in embodiments of the present cracking reactor 106 includeH-ZSM-5 from Zeolyst International.

Some of the F-T products generated by the F-T reactor 104, as well assome of the cracked hydrocarbon products generated by the crackingreactor 106 may be hydrogenated in hydrogenation reactor 108 to produceadditional fluid transportation fuels. The hydrogenation reactor 108includes a hydrogenation catalyst that catalyzes the reaction ofmolecular hydrogen (H₂) from the producer gas with unsaturatedcarbon-carbon bonds in the F-T products (cracked and/or uncracked) toproduce less saturated or unsaturated fluid transport fuels. When theF-T catalyst in the F-T reactor 104 is also catalyzing a WGS reaction,enough molecular hydrogen may be generated so that no additional outsidesource of hydrogen is needed for the hydrogenation reactor 108.

The hydrogenation catalyst may include a palladium or platinumcontaining catalyst, such as 0.5% palladium on alumina. This material iscommercially available from Aldrich Chemical Company (Aldrich No.520675).

Exemplary Methods

FIG. 2 shows a flowchart with selected steps in a method 200 ofconverting carbon-containing feedstocks to fluid transportation fuelsaccording to embodiments of the invention. The method 200 may includethe step of converting a carbon-containing feedstock into a producer gas(202). When the feedstock is a simple alkane such as methane, a partialoxidation of the methane with air produces a syngas (i.e., H₂+CO)diluted in molecular nitrogen, which is the producer gas. Because theC:H ratio in methane is higher than other carbon-feedstocks likebiomass, the CO:H₂ ratio is also higher, and may already be at the 1:2ratio necessary for a sustained F-T reaction step (see Reaction 1).

When feedstocks like biomass are gasified into producer gas, the ratioCO:H₂ is about 1:0.7 and should be adjusted (204) closer to 1:2. Thisadjustment in the ratio may be done by a water-gas-shift (WGS) reactionin the same location as the producer gas is generated, in-situ at thesite of the Fischer-Tropsch reaction, in a separate WGS reactor, or acombination of these locations.

Once the producer gas has about a 1:2 ratio of CO:H₂, either initiallyor with the help of a WGS reaction, at least a portion of the producergas may be converted to F-T products (206) through a catalytic F-Treaction. As noted above, some of the F-T products are fluidtransportation fuels that need no additional conversions or treatments.Other F-T products are too small or too large to be transportationfuels, and a portion of these products may be further converted intoadditional transportation fuels.

These further conversion processes may include catalytically crackingthe F-T products (208). Large, waxy F-T products may be cracked intosmaller fluid transportation fuels, and smaller F-T products may becracked to form alkyl substituted aromatic components of transportationfuels. The conversion processes may also include hydrogenating some ofthe F-T products (210). These may include direct products from the F-Treaction, as well as catalytically cracked products that still have oneor more unsaturated bonds.

The fluid transportation fuels produced by the apparatuses and methodsmay include room temperature liquids and gases used in transportationvehicles, including cars, trucks, boats, and airplanes, among othervehicles. The initial mixture of the fluid transportation fuels emergingfrom the present apparatuses may be separated into refinedtransportation fuels by conventional distillation and refiningtechniques. Because the fuels are relatively low in sulfur and othercontaminants, less scrubber/purifying equipment is needed to make thefinal transportation fuel.

Embodiments may also include methods for converting thecarbon-containing feedstock into predominantly hydrocarbon waxes insteadof fluid transportation fuels. These embodiments may include bypassingthe catalytic cracking and hydrogenation of the F-T products and insteadrecycling them through the site of the F-T reaction one or more times.The additional exposure of the F-T products to a F-T catalyst causesadditional combination of smaller products into larger ones, includingthe hydrocarbon waxes. The heavy liquid and solid waxes may be recoveredfrom a hot wax trap of the apparatus.

Exemplary Systems

Exemplary systems have been demonstrated to operate with compressedproducer gas from the gasification of biomass. These systems were ableto repeatedly shut down, temperature cycle, and restart the productionof fluid FT transport fuels with little or no loss of catalyticactivity. Subsequent separation of the FT products into syngasoline andsyndiesel fractions is easily accomplished by a simple distillationstep.

Exemplary Fischer-Tropsch Reactor Systems

Embodiments of the FT Reactor System may include a fixed-bedbiomass-to-liquid system that operates at relatively low pressures(e.g., about 170 psig to about 240 psig) to make the F-T process moreamenable to small, distributed modular applications. The FT catalystused in the system may be made from an inexpensive iron mineral-basedpowdered substrate capable of doing in-situ water-gas-shift reactions aswell as FTS reactions. This way the gasified biomass is not required topass through a separate WGS reactor to adjust the mole ratio of CO:H₂closer to 1:2.

The preparation of the substrate catalyst may include mixing thesubstrate with a blend of inorganic salt solutions to adjust therelative rate of the WGS reaction compared with the FTS reaction. Theinorganic salts may also be selected to influence the quantities andtypes of FT products that are produced. Preparation may also includereducing the substrate with hydrogen to activate catalytic sites on thesubstrate's surface. In addition, a catalytic-active carbon may bedeposited on the reduced substrate.

The substrate catalyst can take advantage of the 50 vol % molecularnitrogen in producer gas to increase yields of fluid FT transportationfuels. In contrast, conventional FT catalysts are designed to work withpure syngas that contains only CO and H₂ without the molecular nitrogenpresent. The substrate catalyst can convert the producer gas into avariety of FT products, including methane, ethane, propanes, butanes,light olefins (e.g., ethylene, propylene, butelenes, etc.), gasoline,synthetic paraffinic kerosene (SPK), diesel fuels, and waxes, amongother products. Some of these products, such as the waxes and lightolefins, may be converted into additional stable fluid fuels by crackingand/or hydrogenation. Embodiments of present reactor systems may includedownstream reactors for cracking and/or hydrogenation.

Exemplary Cracking Reactor

In a downstream processing step, raw FT products may be sent through apacked bed of a zeolite cracking catalyst to convert high molecularweight waxes to room-temperature liquid fuels, and to condense lightolefins to methyl and ethyl substituted aromatic gasoline and dieselconstituents. The zeolite may be an H-ZSM-5 catalyst from ZeolystInternational for cracking waxes and aromatizing light olefins. TheZSM-5 zeolites were originally developed by Mobil Oil Company in the1970s to crack heavy oils and convert methanol to aromatic gasolineconstituents. The H-ZSM-5 catalyst has demonstrated a reduction in waxyFT hydrocarbons from about 20 wt. % to about 5 wt. %

Exemplary Hydrogenation Reactor

In another downstream processing step, dewaxed liquid fuels from thecracking operations may be sent through a fixed bed of palladiumhydrogenation catalyst to saturate olefinic sites and stabilize theliquid fuel products. A hydrogenation catalyst that contains about 0.5%palladium on alumina (e.g., Aldrich No. 520675) may be used in thehydrogenation reactor. Tests from current operations indicate thepartial pressure of residual hydrogen processed gas (around 12 vol. %)is sufficient to cap-off and stabilize reactive olefin sites.

Analysis of FT Product Distributions

GC/MS analysis of FT products (a.k.a. synfuels) from an embodiment ofthe BTL system show branched hydrocarbons are the major constituents ofthe syngasoline fraction, along with some methyl- and ethyl-substitutedmonocyclic aromatics. The raw syngasoline fraction has a projectedrelatively high octane rating. Like most ultra-low sulfur FT liquidfuels, straight-chain hydrocarbons are the major constituents of CPC'ssynthetic diesel (syndiesel) product. Our syndiesel, however, alsocontains small amounts (e.g., less than 15 wt. %) of methyl- andethyl-monocyclic aromatics from the H-ZSM-5 cracking operations. Thisresults in a FT fuel with a lower cloud point and fewer anticipatedproblems with elastomeric seals than more typical, highly paraffinic F-Tfuels.

Estimated Product Yields:

A bench-top continuous-flow system has demonstrated over 15% conversionof CO in a two-stage simulation, with half the CO consumption for FTproduction of liquid fuels, and the other half used to generate morehydrogen and eliminate waste water via the WGS reaction. Assuming 70% ofthe hydrocarbon products are the gasoline and diesel fuel fractions, theprojected yield of the system is around 42 gallons of synfuels per tonof dry biomass. This quantity of liquid hydrocarbon fuel contains theenergy of about 68 gallons of ethanol.

The CO consumption by the WGS reaction may be reduced by employing ahydrogen-selective to recover and recycle hydrogen from the systemoff-gas and increase the projected yields of liquid fuels by 15% to aprojected 48 gallons of hydrocarbons/ton of dry biomass (equivalent to78 gallons of ethanol per ton).

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the catalyst” includesreference to one or more catalysts and equivalents thereof known tothose skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

1. A method for converting a carbon-containing feedstock into a fluidtransportation fuel, the method comprising: converting thecarbon-containing feedstock into a producer gas comprising H₂, CO, CO₂,and N₂; reacting the producer gas with a substrate catalyst to produce acombination of Fischer-Tropsch (F-T) products, the F-T productsincluding the fluid transportation fuel; catalytically cracking aportion of the F-T products to produce additional amounts of the fluidtransportation fuel; and hydrogenating a portion of the F-T products toproduce additional amounts of the fluid transportation fuel.
 2. Themethod of claim 1, wherein the carbon-containing feedstock comprisesbiomass.
 3. The method of claim 1, wherein the biomass has a watercontent from about 5 wt. % to about 20 wt. %.
 4. The method of claim 1,wherein the carbon-containing feedstock comprises methane.
 5. The methodof claim 1, wherein the fluid transportation fuel is selected from thegroup consisting of gasoline, diesel fuel, aviation fuel, and syntheticparaffinic kerosene.
 6. The method of claim 1, wherein the N₂ comprisesabout 50 mol. % of the producer gas.
 7. The method of claim 1, whereinthe method further comprises increasing the ratio of H₂:CO by having aportion of the producer gas undergo a water-gas-shift (WGS) reaction. 8.The method of claim 7, wherein the WGS reaction is catalyzed by thesubstrate catalyst.
 9. The method of claim 1, wherein the F-T productsare selected from the group consisting of methane, ethane, propanes,butanes, light olefins, gasoline, synthetic paraffinic kerosene,aviation fuel, diesel fuel, and waxes.
 10. The method of claim 9,wherein the light olefins comprise ethylene, propylene, or butelenes.11. The method of claim 1, wherein the step of catalytically cracking aportion of the F-T products comprises: contacting the F-T products witha zeolite catalyst; and splitting an F-T product constituent comprisinga wax into two or more smaller hydrocarbons with the zeolite catalyst;and aromatizing an F-T product constituent comprising a light olefininto an alkyl-aromatic compound.
 12. The method of claim 11, wherein thealkyl-aromatic compound is selected from the group consisting of amethyl-monocyclic aromatic and a ethyl-monocyclic aromatic.
 13. Themethod of claim 1, wherein the step of hydrogenating a portion of theF-T products comprises hydrogenating a hydrocarbon produced by thecatalytic cracking step.
 14. The method of claim 1, wherein the step ofhydrogenating a portion of the F-T products comprises flowing at least aportion of the F-T products through a fixed bed of a hydrogenationcatalyst comprising palladium, platinum, or a combination of palladiumand platinum.
 15. The method of claim 14, wherein the palladiumhydrogenation catalyst comprises about 0.5 wt % palladium on an aluminasubstrate.
 16. The method of claim 1, wherein the step of hydrogenatinga portion of the F-T products comprises exclusively supplying hydrogenfor the hydrogenation from the producer gas.
 17. The method of claim 1,wherein the method further comprises cooling the substrate catalyst witha portion of the N₂ from the producer gas.
 18. The method of claim 1,wherein a pressure for reacting the producer gas with the substratecatalyst is about 250 psig or less.
 19. The method of claim 1, wherein atemperature for reacting the producer gas with the substrate catalyst isabout 250° C. to about 300° C.
 20. An apparatus for converting acarbon-containing feedstock into a fluid transportation fuel, theapparatus comprising: a producer gas reactor operable to convert thecarbon-containing feedstock into a producer gas comprising H₂, CO, CO₂,and N₂; and a Fischer-Tropsch reactor fluidly coupled to the producergas reactor, wherein the Fischer-Tropsch reactor is operable to converta portion of the producer gas into a combination of Fischer-Tropsch(F-T) products, the F-T products including the fluid transportationfuel; a cracking reactor fluidly coupled to the Fischer-Tropsch reactor,wherein the cracking reactor is operable to catalytically crack aportion of the F-T products to produce additional amounts of the fluidtransportation fuel; and a hydrogenation reactor fluidly coupled to thecracking reactor, wherein the hydrogenation reactor is operable tohydrogenate a portion of the F-T products to produce additional amountsof the fluid transportation fuel.
 21. The apparatus of claim 20, whereinthe producer gas reactor is a biomass gasification reactor operable toconvert biomass and air into the producer gas.
 22. The method of claim21, wherein the biomass is selected from the group consisting of woodybiomass, non-woody biomass, a cellulosic product, cardboard, fiberboard, paper, plastic, and a food stuff.
 23. The apparatus of claim 20,wherein the Fischer-Tropsch reactor comprises a cylindrical tube filledwith a Fischer-Tropsch catalyst, wherein the tube has a diameter rangingfrom about 2 inches to about 3.5 inches.
 24. The apparatus of claim 20,wherein the Fischer-Tropsch reactor comprises a Fischer-Tropsch catalystcomprising iron.
 25. The apparatus of claim 20, wherein theFischer-Tropsch reactor comprises as Fischer-Tropsch catalyst operableto catalyze a water-gas-shift reaction between H₂O and CO to produce H₂and CO₂.
 26. The apparatus of claim 20, wherein the cracking reactorcomprises a cracking catalyst comprising a zeolite that cancatalytically crack waxes and aromatize light olefins.
 27. The apparatusof claim 26, wherein the zeolite comprises a ZSM-5 zeolite.
 28. Theapparatus of claim 20, wherein the hydrogenation reactor comprises ahydrogenation catalyst comprising palladium.
 29. The apparatus of claim28, wherein the hydrogenation catalyst comprises palladium on alumina.30. A method for converting a carbon-containing feedstock intohydrocarbon waxes, the method comprising: converting thecarbon-containing feedstock into a producer gas comprising H₂, CO, CO2,and N₂; reacting the producer gas with a substrate catalyst to produce acombination of Fischer-Tropsch (F-T) products, the F-T productsincluding hydrocarbon gases and liquids, and a first portion of thehydrocarbon waxes; and reacting at least a portion of the hydrocarbongases and. liquids with the substrate catalyst to produce a secondportion of the hydrocarbon waxes.